With manufactured semiconductor wafers increasing in size, systems for delivering gases and vapors to process tools, such as vacuum deposition chambers, are required to simultaneously introduce a gas or vapor used in the deposition process into more than one zone of the process tool to insure uniform deposition and high quality processing of each wafer. Maintaining the pressure of the input flow into each zone at the desired pressure is necessary to achieve the desired results. Thus, dual zone pressure controllers are known for providing a flow of a gas or vapor through separately controlled channels into two zones of a process chamber at a controlled pressure. With bigger wafer sizes becoming even more desirable, multiple zone pressure controllers for controlling the pressure of gas or vapors must be designed to provide gas and vapors to more than two zones of a process chamber at a controlled pressure. However, with an increase in the number of zones, there is a need to reduce the costs of manufacturing of the multiple zone pressure controllers as the need for control of more zones becomes necessary. Further effort must also be made to reduce the physical space limitations posed by these controllers.
In implementation, the wafer is positioned on a wafer support and held in place by a vacuum. With larger wafers, the wafer may not form a complete seal around the contact areas between the wafer and the wafer support. As a result there may be some leakage of at one or more of these contact areas, making it difficult to control the pressure of the gas introduced into each of the zones. Currently, a needle valve (called a “leakby” valve) is employed for partially diverting some of the flow of each channel from the inlet flow into a corresponding zone so that the inlet flow pressure of the gas or vapor into each zone can be adjusted so as to maintain the desired pressure of the inlet flow to each zone despite leakage at the contact areas between the wafer support and the wafer.
Thus, leakby needle valves can be used to tweak each channel so as to ensure that the inlet flow to each zone are match from channel to channel for a given same pressure setpoint. This way the flow rates into the various zones of a chamber can be equalized by tweaking the various needle valves. Needle valves, however, are expensive and physically take up space usually in a confined manufacturing area.